Disk tray moving device and disk recording and/or reproducing device

ABSTRACT

The present invention provides a disc tray shift device including a disc tray having at least one disc placement portion, a rack having an arc portion and at least one straight portion, the rack being arranged on the disc tray, and a sun gear, a planet gear which has a large-tooth-portion engaged with the sun gear and a small-tooth-portion engaged with the rack, and a shift mechanism for shifting the disc tray between a position where the disc placement portion is withdrawn externally and a position where the disc placement portion is housed internally, wherein teeth of at least one of the sun gear, the planet gear, and the rack are profile-shifted.

TECHNICAL FIELD

The present invention relates to a disc tray shift device using a gearmechanism having a sun gear and a planet gear, and disc recording and/orreproducing apparatus having the disc tray shift device.

BACKGROUND ART

Conventionally, there have been employed disc players for reproducinginformation recorded on read-only type optical discs, and for recordinginformation to recording type optical discs and reproducing informationrecorded thereon. Such a disc player includes a disc tray onto which aplurality of optical discs are placed for loading, and a tray shiftmechanism for shifting or moving the disc tray internally to andexternally from the main body of the disc player.

The disc tray has the main surface which is provided with a plurality ofdisc placement recesses onto which a plurality of optical discs are tobe placed. The disc tray is so arranged in the disc player as to be ableto shift between a setting/taking-out position where an optical disc isset/taken out onto/from the disc tray and a playback position whereinformation recorded on an optical disc is reproduced.

The tray shift mechanism includes a planetary gear mechanism forshifting the disc tray, and a drive mechanism for driving or rotatingthe planetary gear mechanism.

As shown in FIG. 1, a conventional planetary gear mechanism 200 of thetray shift mechanism includes a sun gear 201 which is driven or rotatedby the drive mechanism, a planet gear 202 which is engaged with the sungear 201, and an inner-tooth-rack 203 substantially of a U shape whichhas teeth provided on the inner side thereof and is engaged with theplanet gear 202.

The sun gear 201 has a pivot shaft 205 at the center thereof, and iscaused to rotate along with the pivot shaft 205 when the pivot shaft 205is driven or rotated by a motor, not shown, of the drive mechanism.

The planet gear 202 has a pivot shaft 206 at the center thereof, and hasa large-tooth-portion 207 which is engaged with the sun gear 201, and asmall-tooth-portion 208 which has a pitch circle smaller than that ofthe large-tooth-portion 207 and is engaged with the inner-tooth-rack203.

The inner-tooth-rack 203 is unitedly formed at around the rear end ofthe disc tray, and is engaged with the small-tooth-portion 208 of theplanet gear 202.

The disc tray is provided with a guide ditch 211 for guiding the planetgear 202 inside and along the inner-tooth-rack 203, in which the pivotshaft 206 is movably arranged. That is, the revolution operation of theplanet gear 202 is assisted by the guide ditch 211 with thesmall-tooth-portion 208 thereof engaged with the inner-tooth-rack 203.

In thus configured planetary gear mechanism 200, when the sun gear 201is caused to rotate by the drive mechanism, not shown, thelarge-tooth-portion 207 of the planet gear 202 is rotated. When thelarge-tooth-portion 207 of the planet gear 202 is rotated, thesmall-tooth-portion 208 of the planet gear 202 is rotated along theinner-tooth-rack 203, while concurrently the planet gear 202 is causedto revolve around the sun gear 201 with the pivot shaft 205 being itsrevolution center.

Thus, in the planetary gear mechanism 200, when the small-tooth-portion208 of the planet gear 202 is rotated, the inner-tooth-rack 203 isshifted, which causes the disc tray having the inner-tooth-rack 203 toshift between the setting/taking-out position and the playback position.

Generally, in a gear mechanism, in case of using gears made of resin,the distance between the centers of a pair of gears which are engagedwith each other is so designed as to be slightly larger than the sum ofradiuses of pitch circles of the respective gears. This is to cope withor prevent interference such as clog between respective gears due toerror of negative value which may arise between centers of formed gearsor expansion of gears with heat.

On the other hand, in the conventional planetary gear mechanism 200 ofthe tray shift mechanism, the center of an arc portion of theinner-tooth-rack 203 coincides with that of the sun gear 201, andengaged points between the respective gears are aligned on a straightline 1, as shown in FIG. 1. Thus, when it is assumed that r₃ is a pitchcircle radius of the sun gear 201, r₄ is a pitch circle radius of theplanet gear 202, and λ is a predetermined gap, it is difficult to designthe sun gear 201 and the planet gear 202 such that the distance betweenthe centers of the gears is set to be (r₃+r₄+λ) by adding thepredetermined gap λ to the sum of the r₃ and the r₄ in order to preparegears of desired modules or desired number of teeth having appropriategap or spacing therebetween, as shown in FIG. 2.

In preparing gears of the planetary gear mechanism 200, it is thesimplest way to make the distance between the centers of the sun gear201 and the planet gear 202 equal to the sum of the pitch circleradiuses of the respective gears in view of designing of modules ornumber of teeth.

However, in reality, in case the predetermined gap λ is not secured, theproblem of interference such as clog between respective gears which iscaused by a slight change in condition or environment arises.

Furthermore, in the planetary gear mechanism 200, it is required thatgears of sufficiently large modules be arranged in the limited space ofthe main body of the disc player.

DISCLOSURE OF THE INVENTION

Accordingly, the present invention has an object to overcome theabove-mentioned drawbacks of the prior art by providing a disc trayshift device using a small-sized gear mechanism which can preventinterference of gear rotation of gears engaged with each other andimprove operation reliability, and disc recording and/or reproducingapparatus having the disc tray shift device.

The above object can be attained by providing a disc tray shift deviceincluding a disc tray having at least one disc placement portion, a rackhaving an arc portion and at least one straight portion., the rack beingarranged on the disc tray, and a sun gear, a planet gear which has alarge-tooth-portion engaged with the sun gear and a small-tooth-portionengaged with the rack, and a shift mechanism for shifting the disc traybetween a position where the disc placement portion is withdrawnexternally and a position where the disc placement portion is housedinternally, wherein teeth of at least one of the sun gear, the planetgear, and the rack are profile-shifted.

Also, the above object can be attained by providing a gear mechanismincluding a sun gear, at least one planet gear which has asmall-tooth-portion, and a large-tooth-portion engaged with the sungear, the small-tooth-portion and the large-tooth-portion being rotatedunitedly, and a rack for causing the planet gear to revolve around thesun gear when the sun gear is rotated, the rack being engaged with thesmall-tooth-portion, wherein teeth of at least one of the sun gear, theplanet gear, and the rack are profile-shifted.

Also, the above object can be attained by providing a disc recordingand/or reproducing apparatus including a disc tray having at least onedisc placement portion, a recording and/or reproducing unit forrecording and/or reproducing information to and/or from a disc placed onthe disc placement portion, a rack having an arc portion and at leastone straight portion, the rack being arranged on the disc tray, and asun gear, a planet gear which has a large-tooth-portion engaged with thesun gear and a small-tooth-portion engaged with the rack, and a shiftmechanism for shifting the disc tray between a position where the discplaced on the disc placement portion is replaceable and a position whereinformation is recorded and/or reproduced to and/or from the disc,wherein teeth of at least one of the sun gear, the planet gear, and therack are profile-shifted.

The distance between the centers of the sun gear and thelarge-tooth-portion is set to be (r₁+r₂), and a predetermined gap λ issecured between pitch circles of the sun gear and thelarge-tooth-portion, where the (r₁+r₂) is the sum of a pitch circleradius of the sun gear, a pitch circle radius of thelarge-tooth-portion, and the predetermined gap λ.

The pitch circle radius of the sun gear is set to be (r₁−x λ), while thepitch circle radius of the large-tooth-portion is set to be {r₂−(1−x)λ},where the x is a predetermined coefficient.

These objects and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription of the preferred embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of a conventional planetary gear mechanism.

FIG. 2 shows a plan view for explaining the distance between the centersof gears of the planetary gear mechanism shown in FIG. 1.

FIG. 3 shows a perspective view of a disc player according to thepresent invention.

FIG. 4 shows a perspective view of a disc tray used in the disc player.

FIG. 5 shows a plan view of a tray shift mechanism for shifting the disctray.

FIG. 6 shows a plan view of a sun gear, a planet gear, and aninner-tooth-rack arranged in the tray shift mechanism.

FIG. 7 shows a plan view of the tray shift mechanism, in which the slidetray is shifted along the direction of an arrow A₂.

FIG. 8 shows a plan view of the tray shift mechanism, in whichinformation is reproduced from an optical disc.

FIG. 9 shows a plan view of the tray shift mechanism, in which the slidetray is shifted along the direction of the arrow A₂ while playbackoperation for the optical disc is being performed.

FIG. 10 shows a plan view for explaining the distance between thecenters of the sun gear and the planet gear.

FIG. 11A and FIG. 11B show plan views for explaining the engagementstate between a small-tooth-portion of the planet gear and theinner-tooth-rack, where FIG. 11A shows the case in which teeth thereofare not profile-shifted, while FIG. 11B shows the case in which teeththereof are profile-shifted.

FIG. 12 shows a plan view of another example of the planetary gearmechanism according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The disc player employing the present invention will further bedescribed below concerning the best modes with reference to theaccompanying drawings.

The disc player 1 according to the present invention includes a disctray 11 onto which a plurality of optical discs 5 are to be placed, aslide tray 12 for rotatably supporting the disc tray 11, a tray shiftmechanism 13 for shifting the slide tray 12 along the directions ofarrows A₁ and A₂, and a tray rotation drive mechanism 14 for driving orrotating the disc tray 11, as shown in FIG. 3 and FIG. 4.

The disc player 1 includes a disc rotation drive mechanism 15 fordriving or rotating the optical disc 5, a reproduction mechanism 16 forreproducing information recorded on the optical disc 5, a clampmechanism 17 for rotatably clamping the optical disc 5, a support stand18 for supporting the disc rotation drive mechanism 15 and thereproduction mechanism 16, a support base 19 for supporting the clampmechanism 17 and the support stand 18, and a pivot mechanism 20 forcausing the support stand 18 to pivot toward and away from the clampmechanism 17, as shown in FIG. 4 and FIG. 5.

The disc tray 11 is substantially of a disc shape, and is rotatablysupported by the slide tray 12 with a rotation shaft 24 being itsrotation center, as shown in FIG. 4. The disc tray 11 has the mainsurface which is provided with a plurality of disc placement recesses 26onto which a plurality of optical discs 5 are to be placed along theouter circumference thereof.

Each of the disc placement recesses 26 is provided with an opening 27for causing the disc rotation drive mechanism 15 to face a center holeof the optical disc 5 to drive the optical disc 5. The opening 27 has apositioning cut 28 for positioning the disc placement recess 26 towardthe disc rotation drive mechanism 15. The disc placement recess 26 hasan opening 29 for causing the reproduction mechanism 16 to face theoptical disc 5 to reproduce information recorded thereon, which spreadsout from the opening 27 to the outer circumference of the disc tray 11.

The slide tray 12 is made of resin, and is substantially of arectangular shape, and has a tray placement recess 31 on the mainsurface thereof onto which the disc tray 11 is rotatably placed, asshown in FIG. 4. The slide tray 12 has a guide member 32 at one sidethereof parallel to the A₁ and A₂ directions. The slide tray 12 has theguide member 32 held by a guide rail, not shown, arranged on the supportbase 19, enabling the slide tray 12 to slide along the A₁ and A₂directions.

The tray shift mechanism 13 includes a planetary gear mechanism 35 forshifting the slide tray 12 along the A₁ and A₂ directions, and a drivemechanism 36 for driving or rotating the planetary gear mechanism 35, asshown in FIG. 3, FIG. 4, and FIG. 5.

As shown in FIG. 5 and FIG. 6, the planetary gear mechanism 35 includesa sun gear 41 which is driven or rotated by the drive mechanism 36, aplanet gear 42 which is engaged with and to be rotated by the sun gear41, and an inner-tooth-rack 43 substantially of a U shape which hasteeth provided on the inner side thereof and is engaged with the planetgear 42.

The sun gear 41 is made of resin, and has a pivot shaft 45 unitedlyformed at the center thereof which is arranged on the support base 19,allowing the sun gear 41 to pivot with the pivot shaft 45 being itspivot center, as shown in FIG. 6. The sun gear 41 is caused to rotatealong with the pivot shaft 45 when the pivot shaft 45 is rotated by thedrive mechanism 36.

The planet gear 42 is made of resin, and has a pivot shaft 46 unitedlyformed at the center thereof, as shown in FIG. 6. The planet gear 42 hasa large-tooth-portion 47 which is engaged with the sun gear 41, and asmall-tooth-portion 48 which has a pitch circle smaller than that of thelarge-tooth-portion 47 and is engaged with the inner-tooth-rack 43.

The inner-tooth-rack 43 is unitedly formed at around the rear end of theslide tray 12, and has straight rail portions 51, 52 which are parallelto each other and an arc rail portion 53 whose ends are connected torespective ends of the straight rail portions 51, 52, forming asuccessive rail portion, as shown in FIG. 5 and FIG. 6. The straightrail portions 51, 52 of the inner-tooth-rack 43 are so formed as to beparallel to the shift direction of the slide tray 12. The straight railportion 52 which is located at the right side is formed longer than thestraight rail portion 51 which is located at the left side, and thestraight rail portions 51, 52 extend toward the rear end of the slidetray 12, the straight rail portion 52 extending a little bit furtherthan the straight rail portion 51, as shown in FIG. 5.

The slide tray 12 is provided with a guide ditch 55 for guiding theplanet gear, 42 inside and along the inner-tooth-rack 43, in which thepivot shaft 46 is movably arranged. That is, the revolution operation ofthe planet gear 42 is assisted by the guide ditch 55 with thesmall-tooth-portion 48 thereof engaged with the inner-tooth-rack 43.

The planetary gear mechanism 35 of the tray shift mechanism 13 shiftsthe slide tray 12 so that the disc tray 11 is caused to shift between asetting/taking-out position where the optical disc 5 is set/taken outonto/from the disc tray 11 and a playback position where informationrecorded on the optical disc 5 is reproduced by means of the sun gear 41and the planet gear 42.

The drive mechanism 36 of the tray shift mechanism 13 includes a largepulley 76 for rotating the sun gear 41 of the planetary gear mechanism35, a small pulley 77 for rotating the large pulley 76, a belt 78 fortransmitting drive force of the small pulley 77 to the large pulley 76which is extended between the two pulleys, and a motor 79 for driving orrotating the small pulley 77, as shown in FIG. 5.

The large pulley 76 is fixed to the pivot shaft 45 of the sun gear 41.The motor 79 is arranged on the support base 19, and the small pulley 77is fixed to a rotation shaft 80 of the motor 79. Thus, in the drivemechanism 36, when the motor 79 drives or rotates the small pulley 77,the sun gear 41 of the planetary gear mechanism 35 is caused to rotateby means of the small pulley 77, large pulley 76, and belt 78 beingextended therebetween.

The tray rotation drive mechanism 14 is arranged on the bottom of theslide tray 12, and includes a rotation shaft 24 for rotatably holdingthe disc tray 11, a gear, not shown, engaged with the rotation shaft 24,and a motor 25 for driving or rotating the gear, as shown in FIG. 4. Thetray rotation drive mechanism 14 drives or rotates the disc tray 11supported by the slide tray 12 in the tray placement recess 31 torelocate a desired one of the disc placement recesses 26 to the frontside of the slide tray 12, which facilitates the setting/taking-outoperation for the optical disc 5 onto/from the disc tray 11. Then, thetray rotation drive mechanism 14 relocates the optical disc 5 placed onone of the disc placement recesses 21 to a position between or facingthe disc rotation drive mechanism 15 and the reproduction mechanism 16.

The disc rotation drive mechanism 15 includes a disc table 81 onto whichthe optical disc 5 is to be placed for loading, and a spindle motor 82for driving or rotating the disc table 81, as shown in FIG. 5. The disctable 81 is substantially of a cylindrical shape, and is made ofmetallic material having magnetism. The disc table 81 has a discplacement member in the shape of a flange at the outer circumference ofone cylinder end thereof, onto which the optical disc 5 is to be placed.Also, at the same cylinder end, the disc table 81 has an engagementmember 84 substantially of a cylindrical shape at the innercircumference thereof, which is to be engaged with a center hole of theoptical disc 5. The spindle motor 82 has a spindle shaft 85 at which thedisc table 81 is arranged, which penetrates the disc table 81. The endof the spindle shaft 85 protrudes from the top surface of the engagementmember 84 of the disc table 81.

The reproduction mechanism 16 includes an optical pickup 88 forreproducing information recorded on the optical disc 5, and a shiftmechanism 89 for causing the optical pickup 88 to shift along the radialdirection of the optical disc 5, as shown in FIG. 5. The optical pickup88 includes an optical unit which has an objective lens for causing alaser beam to focus on the recording surface of the optical disc 5, anda lens shift unit for driving or shifting the objective lens alongdirections parallel to and perpendicular to the optical axis thereof,respectively. The shift mechanism 89 has a support base for supportingthe optical pickup 88, guide shafts for holding the support base suchthat the support base can shift along the radial direction of theoptical disc 5, and a thread motor for causing the support base toshift, not shown.

The clamp mechanism 17 includes a clamp member 91 for rotatably clampingthe optical disc 5, a clamp plate 92 in the shape of a disc which is tobe abutted to the optical disc 5, and an operation arm 93 for causingthe clamp member 91 to shift toward and away from the disc table 81, asshown in FIG. 5. The clamp member 91 is substantially of a cylindricalshape, and includes the clamp plate 92 at the outer circumference of onecylinder end thereof facing the disc table 81. The operation arm 93holds the clamp member 91 at the end thereof, and has pivot shafts, notshown, at substantially the halfway portion along the longitudinaldirection thereof, which are held by the support base 19, and allow theoperation arm 93 to pivot upward and downward.

The support stand 18 is substantially of a rectangular block shape, andthe disc rotation drive mechanism 15 and the reproduction mechanism 16are so arranged on the main surface of the support stand 18 as to facethe clamp mechanism 17, respectively, as shown in FIG. 5. The supportstand 18 has pivot shafts 97, 97 at one end thereof, which are held bythe support base 19 and allow the support stand 18 to pivot upward anddownward. The support stand 18 has, at the same end, an operationmember, not shown, for operating the operation arm 93 of the clampmechanism 17, which is unitedly and extendedly formed toward the basalportion of the operation arm 93.

The support stand 18 has an engagement element 98 at the other endthereof, which is engaged with the pivot mechanism 20, as shown in FIG.5. And, the support stand 18 is caused to pivot upward and downward bythe pivot mechanism 20 via the engagement element 98. The support stand18 has a positioning shaft 99 on the main surface thereof forpositioning the optical disc 5 placed on each disc placement recess 26toward the disc table 81 when the positioning shaft 99 is engaged withthe positioning cut 28 of each disc placement recess 26 of the disc tray11. Thus, the optical disc 5 placed on each disc placement recess 26 ofthe disc tray 11 driven or rotated by the tray rotation drive mechanism14 is positioned toward the disc table 81.

The support base 19 is substantially of a U shape in its cross section,not shown, and has a main base 101 for slidably supporting the slidetray 12 along the A₁ and A₂ directions, a rear member 102 which holdsthe pivot shafts 97, 97 for allowing the support stand 18 to pivotupward and downward, and a ceiling member 103 which holds the pivotshafts for allowing the operation arm 93 to pivot upward and downward,as shown in FIG. 4 and FIG. 5. The main base 101 of the support base 19is provided with an opening, not shown, in which the support stand 18 isso arranged as to be able to pivot upward and downward.[1]

The pivot mechanism 20 includes a cam 110 for causing the support stand18 to pivot upward and downward, and an idler wheel 111 for rotating thecam 110, and an interlock shaft 112 arranged at the pivot shaft 45 ofthe sun gear 41 of the planetary gear mechanism 35, and the pivotmechanism 20 interlocks together with the tray shift mechanism 13, asshown in FIG. 5. The pivot mechanism 20 further includes a rotaryencoder 117 for detecting revolution angle of the planet gear 42, whichis arranged at the pivot shaft 45 of the sun gear 41. When the planetgear 42 performs the revolution operation, the rotary encoder 117 isconcurrently rotated, and thus can detect the state of shift operationof the slide tray 12.

The cam 110 is so arranged on the support base 19 as to be able to pivotwith a pivot shaft 113 being its pivot center, and has a cam ditch, notshown, for shifting the engagement element 98 of the support stand 18 atthe outer circumference thereof. When the cam 110 is rotated, thesupport stand 18 is caused to pivot toward and away from the clampmember 91 of the clamp mechanism 17 by means of the engagement element98 arranged in the cam ditch. That is, when the support stand 18 pivotsupward, the optical disc 5 placed on the disc table 81 is clamped by thedisc table 81 and the clamp plate 92 of the clamp member 91. Also, whenthe support stand 18 pivots downward, the clamp state of the opticaldisc 5 clamped by the disc table 81 and the clamp plate 92 of the clampmember 91 is released.

The idler wheel 111 is so arranged on the support base 19 as to be ableto pivot with a pivot shaft 114 being its pivot center, and has itsouter circumference caused to come into contact with the outercircumference of the cam 110.

Next, the operation of the tray shift mechanism 13 of the disc player 1for shifting the slide tray 12 along the A₁ and A₂ directions will beexplained with reference to the drawings.

In the tray shift mechanism 13, the slide tray 12 shown in FIG. 5 ishoused to be located at the playback position in the disc player 1 afterbeing shifted along the A₁ direction. In this state, the planet gear 42of the planetary gear mechanism 35 is located at the left side positionof the center of the arc rail portion 53 of the inner-tooth-rack 43 withthe small-tooth-portion 48 thereof engaged with the inner-tooth-rack 43,as shown in FIG. 5. Also, in this state, the disc rotation drivemechanism 15 and the reproduction mechanism 16 arranged on the supportstand 18 are located at a position apart from the slide tray 12.

When the small pulley 77 of the drive mechanism 36 is driven or rotatedby the motor 79 clockwise, the large pulley 76 is rotated by the belt 78which transmits drive force of the small pulley 77 to the large pulley76, which causes the sun gear 41 to rotate clockwise, while concurrentlythe planet gear 42 is caused to revolve around the sun gear 41 clockwisealong the arc rail portion 53 of the inner-tooth-rack 43 from a positionshown in FIG. 5. Then, the planet gear 42 is shifted to the connectionpoint of the straight rail portion 51 and the arc rail portion 53 of theinner-tooth-rack 43 to be engaged with the straight rail portion 51.After the planet gear 42 is engaged with the straight rail portion 51 ofthe inner-tooth-rack 43, rotation force of the planet gear 42 istransmitted to the straight rail portion 51 of the inner-tooth-rack 43with the planet gear 42 staying at the same position, which causes theslide tray 12 to shift along the A₂ direction.

Then, the end of the straight rail portion 51 of the inner-tooth-rack 43comes to the planet gear 42, as shown in FIG. 7, and thus the slide tray12 is withdrawn to be located at the setting/taking-out position. Thus,in this state, part of the disc placement recesses 26 of the disc tray11 having the optical discs 5 placed thereon is withdrawn from the discplayer 1, which enables the setting/taking-out operation for the opticaldisc 5 onto/from the disc tray 11 under rotation of the disc tray 11, asshown in FIG. 3.

When the slide tray 12 is located at the setting/taking-out position,the disc rotation drive mechanism 15 and the reproduction mechanism 16are located at a position apart from the disc tray 11.

Next, when the small pulley 77 of the drive mechanism 36 is driven orrotated by the motor 79 counterclockwise, the slide tray 12 is caused toshift along the A₁ direction to be housed in the disc player 1. When theslide tray 12 is located at the playback position, the connection pointof the straight rail portion 51 and the arc rail portion 53 of theinner-tooth-rack 43 comes to the planet gear 42, and the planet gear 42is shifted from the straight rail portion 51 to the arc rail portion 53.Then, the planet gear 42 is caused to revolve around the sun gear 41counterclockwise along the arc rail portion 53 of the inner-tooth-rack43, as shown in FIG. 5.

When the planet gear 42 is caused to revolve counterclockwise, theinterlock shaft 112 of the pivot mechanism 20 is rotated along with therevolution operation of the planet gear 42. At this time, rotation forceof the interlock shaft 112 is transmitted to the cam 110 via the idlerwheel 111, which caused the cam 110 to rotate.

When the cam 110 of the pivot mechanism 20 is caused to rotate, theengagement element 98 of the support stand 18 is shifted along the camditch. And when the planet gear 42 is located at the right side positionof the center of the arc rail portion 53 of the inner-tooth-rack 43, asshown in FIG. 8, the support stand 18 is caused to pivot upward with thepivot shafts 97, 97 being its pivot center. Then, the optical disc 5 isplaced onto the disc table 81 of the disc rotation drive mechanism 15,and then the optical disc 5 is rotatably clamped by the disc table 81and the clamp plate 92 of the clamp member 91, in which stateinformation recorded on the optical disc 5 can be reproduced.

At this time, the rotary encoder 117, which is rotated along with therevolution operation of the planet gear 42, detects the shift operationstate of the slide tray 12 and the clamp operation state for the opticaldisc 5 by the pivot mechanism 20. And when the planet gear 42 comes to aposition shown in FIG. 8, drive or rotation operation of the motor 79 ofthe drive mechanism 36 is suspended.

Then, the optical pickup 88 of the reproduction mechanism 16 is causedto shift along the radial direction of the optical disc 5, andinformation recorded on the optical disc 5 can be reproduced.

Furthermore, at the time information recorded on the optical disc 5 isbeing reproduced, it is possible to shift the slide tray 12 to thesetting/taking-out position to replace the optical discs 5 with otherones.

That is, when the small pulley 77 of the drive mechanism 36 is driven orrotated by the motor 79 counterclockwise at the time when informationrecorded on the optical disc 5 is being reproduced, the planet gear 42is caused to revolve around the sun gear 41 counterclockwise along thearc rail portion 53 of the inner-tooth-rack 43 from a position shown inFIG. 8. Then, the planet gear 42 is shifted to the connection point ofthe straight rail portion 52 and the arc rail portion 53 of theinner-tooth-rack 43 to be engaged with the straight rail portion 52.

After the planet gear 42 is engaged with the straight rail portion 52 ofthe inner-tooth-rack 43, rotation force of the planet gear 42 istransmitted to the straight rail portion 52 of the inner-tooth-rack 43with the planet gear 42 staying at the same position, which causes theslide tray 12 to shift along the A₂ direction.

Then, the end of the straight rail portion 52 of the inner-tooth-rack 43comes to the planet gear 42, as shown in FIG. 9, and thus the slide tray12 is withdrawn to be located at the setting/taking-out position. Thus,the disc placement recesses 26 of the disc tray 11 having the opticaldiscs 5 placed thereon are withdrawn from the disc player 1. In thiscase, since the straight rail portion 52 is formed longer than thestraight rail portion 51, the slide tray 12 is caused to shift along theA₂ direction a little bit further than the case shown in FIG. 7 in whichplayback operation is not being performed.

That is, the slide tray 12 is caused to shift along the A₂ direction alittle bit further so that the playback operation of the optical disc 5is not prevented by the disc tray 11 at the time of replacing theoptical discs 5 on the disc tray 11 with other ones when the disc tray11 on the slide tray 12 is being rotated by the tray rotation drivemechanism 14.

In the planetary gear mechanism 35 of the tray shift mechanism 13, thedistance between the centers of the sun gear 41 and thelarge-tooth-portion 47 of the planet gear 42 is set to be (r₁+r₂), and apredetermined gap λ is secured between pitch circles of the sun gear 41and the large-tooth-portion 47 of the planet gear 42, where the (r₁+r₂)is the sum of a pitch circle radius of the sun gear 41, a pitch circleradius of the large-tooth-portion 47 of the planet gear 42, and thepredetermined gap λ, as shown in FIG. 10. In the planetary gearmechanism 35, teeth of the sun gear 41 and teeth of thelarge-tooth-portion 47 of the planet gear 42 are negativelyprofile-shifted by a predetermined amount.

That is, in the planetary gear mechanism 35 in which the distancebetween the centers of the sun gear 41 and the large-tooth-portion 47 ofthe planet gear 42 is set to be (r₁+r₂), in order to secure thepredetermined gap λ between pitch circles of the sun gear 41 and thelarge-tooth-portion 47 of the planet gear 42, the pitch circle radius ofthe sun gear 41 is set to be (r₁−xλ), while the pitch circle radius ofthe large-tooth-portion 47 of the planet gear 42 is set to be{r₂−(1−x)λ}, where x is a predetermined coefficient.

In the planetary gear mechanism 35, at least either teeth of thesmall-tooth-portion 48 of the planet gear 42 or teeth of theinner-tooth-rack 43 are negatively profile-shifted or positivelyprofile-shifted. The engagement state between the small-tooth-portion 48of the planet gear 42 and the inner-tooth-rack 43 will be explained withreference to the drawings.

In case teeth of the small-tooth-portion 48 of the planet gear 42 andteeth of the inner-tooth-rack 43 are not profile-shifted, since theyinterfere each other and clog is prone to arise, the engagement statebetween them is not desirable, as shown in FIG. 11A. That is, since thenumber of teeth of the small-tooth-portion 48 is smaller that of theinner-tooth-rack 43, the small-tooth-portion 48 of the planet gear 42and the inner-tooth-rack 43 interfere each other.

On the other hand, in case teeth of the small-tooth-portion 48 of theplanet gear 42 and teeth of the inner-tooth-rack 43 are negativelyprofile-shifted by a predetermined amount, since interference of innerteeth or involute interference can be prevented, interference betweenrespective gears can be prevented, as shown in FIG. 11B. In theembodiment, teeth of the small-tooth-portion 48 of the planet gear 42are negatively profile-shifted, while teeth of the inner-tooth-rack 43are positively profile-shifted.

Thus, in the planetary gear mechanism 35, since teeth of the sun gear 41and teeth of the large-tooth-portion 47 of the planet gear 42 areprofile-shifted, the engagement state between the sun gear 41 and thelarge-tooth-portion 47 of the planet gear 42 is improved. Thus,interference such as clog between respective gears due to error whichmay arise between centers of the gears or expansion of gears with heatcan be prevented, which can improve operation reliability sufficiently.

In the above-described planetary gear mechanism 35 of the tray shiftmechanism 13, teeth of the sun gear 41 and teeth of thelarge-tooth-portion 47 of the planet gear 42 are negativelyprofile-shifted. Furthermore, it can also be possible that teeth of thesmall-tooth-portion 48 of the planet gear 42 are negativelyprofile-shifted, while teeth of the inner-tooth-rack 43 are positivelyprofile-shifted.

In the planetary gear mechanism 35, teeth of the sun gear 41 and teethof the planet gear 42 are negatively profile-shifted. On the other band,teeth of a sun gear and teeth of a plurality of planet gears in anotherplanetary gear mechanism may be profile-shifted.

For example, as shown in FIG. 12, another planetary gear mechanism 60includes a sun gear 61, a first planet gear 62 and a second planet gear63 which are engaged with the sun gear 61, and an inner-tooth-gear 64which has teeth provided on the inner side thereof and is engaged withthe first planet gear 62 and the second planet gear 63.

The sun gear 61 is so arranged as to be able to pivot with a pivot shaft66 being its pivot center. The first planet gear 62 has a pivot shaft 67at its center portion, a large-tooth-portion 71, and asmall-tooth-portion 72 whose pitch circle is smaller than that of thelarge-tooth-portion 71, as shown in FIG. 12. Also, the second planetgear 63 has a pivot shaft 68 at its center portion, alarge-tooth-portion 73, and a small-tooth-portion 74 whose pitch circleis smaller than that of the large-tooth-portion 73. The rotation centerof the inner-tooth-gear 64 coincides with that of the sun gear 61.

In the planetary gear mechanism 60, teeth of the sun gear 61, teeth ofthe large-tooth-portions 71, 73 of the first and second planet gears 62,63 are negatively profile-shifted. Thus, predetermined gaps are securedin the distance between the centers of the sun gear 61 and thelarge-tooth-portion 71 of the first planet gear 62, and in the distancebetween the centers of the sun gear 61 and the large-tooth-portion 73 ofthe second planet gear 63. Furthermore, in the planetary gear mechanism60, it can also be possible that, in order to secure predetermined gapsin the distance between the centers of the small-tooth-portion 72 of thefirst planet gear 62 and the inner-tooth-gear 64, and in the distancebetween the centers of the small-tooth-portion 74 of the second planetgear 63 and the inner-tooth-gear 64, teeth of the small-tooth-portions72, 74 of the first and second planet gears 62, 63 are negativelyprofile-shifted, while teeth of the inner-tooth-gear 64 are positivelyprofile-shifted.

In thus configured planetary gear mechanism 60, when the sun gear 61 isdriven or rotated by a motor, not show, the large-tooth-portions 71, 73of the first and second planet gears 62, 63 are rotated. When thelarge-tooth-portions 71, 73 are rotated, the small-tooth-portions 72, 74of the first and second planet gears 62, 63 are rotated, while revolvingaround the sun gear 61 with the pivot shaft 66 being its revolutioncenter. Then, the inner-tooth-gear 64 is caused to rotate.

As in the above, according to the disc player 1 of the presentinvention, in the planetary gear mechanism 35 of the tray shiftmechanism 13, teeth of the sun gear 41 and teeth of thelarge-tooth-portion 47 of the planet gear 42 are negativelyprofile-shifted. Thus, a gap between the pitch circles of the sun gear41 and the large-tooth-portion 47 of the planet gear 42 can be securedsufficiently. So, interference such as clog between the sun gear 41 andthe planet gear 42 can be prevented, thereby improving operationreliability sufficiently.

In the disc tray shift device using the tray shift mechanism 13, sinceteeth of the respective gears are profile-shifted, gears of sufficientlylarge modules can be arranged in the limited space of the main body ofthe disc player 1 with respective pitch circle radiuses set to beconstant, thereby improving operation reliability sufficiently.

Furthermore, the present invention is not limited to the above-describeddisc player, and is applicable to recording and/or reproducingapparatuses using discs such as optical discs as information recordingmedia.

INDUSTRIAL APPLICABILITY

As in the above, according to the gear mechanism of the presentinvention, interference between respective gears can be prevented, andthus operation reliability can be improved sufficiently. So, the disctray shift device and the disc recording and/or reproducing apparatushaving the disc tray shift device can be reduced in size.

According to the disc tray shift device using the above-described trayshift mechanism, interference between respective gears can be prevented.So, operation reliability can be improved sufficiently.

1. A disc tray shift device comprising: a disc tray having at least onedisc placement portion; a rack having an arc portion and at least onestraight portion, the rack being arranged on the disc tray; and a sungear, a planet gear which has a large-tooth-portion engaged with the sungear and a small-tooth-portion engaged with the rack, and a shiftmechanism for shifting the disc tray between a position where the discplacement portion is withdrawn externally and a position where the discplacement portion is housed internally; wherein teeth of at least one ofthe sun gear, the planet gear, and the rack are negativelyprofile-shifted.
 2. The disc tray shift device as set forth in claim 1,wherein teeth of the sun gear and teeth of the large-tooth-portion arenegatively profile-shifted.
 3. The disc tray shift device as set forthin claim 1, wherein teeth of the small-tooth-portion are negativelyprofile-shifted, and teeth of the rack are positively profile-shifted.4. A gear mechanism comprising: a sun gear; at least one planet gearwhich has a small-tooth-portion, and a large-tooth-portion engaged withthe sun gear, the small-tooth-portion and the large-tooth-portion beingrotated unitedly; and a rack for causing the planet gear to revolvearound the sun gear when the sun gear is rotated, the rack being engagedwith the small-tooth-portion; wherein teeth of at least one of the sungear, the planet gear, and the rack are negatively profile-shifted. 5.The gear mechanism as set forth in claim 4, wherein teeth of the sungear and teeth of the large-tooth-portion are negativelyprofile-shifted.
 6. The gear mechanism as set forth in claim 4, whereinteeth of the small-tooth-portion are negatively profile-shifted, andteeth of the rack are positively profile-shifted.
 7. A disc recordingand/or reproducing apparatus comprising: a disc tray having at least onedisc placement portion; a recording and/or reproducing unit forrecording and/or reproducing information to and/or from a disc placed onthe disc placement portion; a rack having an arc portion and at leastone straight portion, the rack being arranged on the disc tray; and asun gear, a planet gear which has a large-tooth-portion engaged with thesun gear and a small-tooth-portion engaged with the rack, and a shiftmechanism for shifting the disc tray between a position where the discplaced on the disc placement portion is replaceable and a position whereinformation is recorded and/or reproduced to and/or from the disc;wherein teeth of at least one of the sun gear, the planet gear, and therack are negatively profile-shifted.
 8. The disc recording and/orreproducing apparatus as set forth in claim 7, wherein teeth of the sungear and teeth of the large-tooth-portion are negativelyprofile-shifted.
 9. The disc recording and/or reproducing apparatus asset forth in claim 7, wherein teeth of the small-tooth-portion arenegatively profile-shifted, and teeth of the rack are positivelyprofile-shifted.
 10. The A disc recording and/or reproducing apparatuscomprising: a disc tray having at least one disc placement portion; arecording and/or reproducing unit for recording and/or reproducinginformation to and/or from a disc placed on the disc placement portion;a rack having an arc portion and at least one straight portion, the rackbeing arranged on the disc tray; and a sun gear, a planet gear which hasa large-tooth-portion engaged with the sun gear and asmall-tooth-portion engaged with the rack, and a shift mechanism forshifting the disc tray between a position where the disc placed on thedisc placement portion is replaceable and a position where informationis recorded and/or reproduced to and/or from the disc; wherein teeth ofat least one of the sun gear, the planet gear, and the rack areprofile-shifted, and wherein the distance between the centers of the sungear and the large-tooth-portion is set to be (r₁+r₂), and apredetermined gap λ is secured between pitch circles of the sun gear andthe large-tooth-portion, the (r₁+r₂) being the sum of a pitch circleradius of the sun gear, a pitch circle radius of thelarge-tooth-portion, and the predetermined gap λ.
 11. The disc recordingand/or reproducing apparatus as set forth in claim 10, wherein the pitchcircle radius of the sun gear is set to be (r₁−xλ), while the pitchcircle radius of the large-tooth-portion is set to be {r₂−(1−x)λ}, the xbeing a predetermined coefficient.